Stars in the southern hemisphere were of course unknown to
European astronomers because no one had travelled there before the 1400s. This
is why most of the constellations in this part of the sky are referred to as
modern constellations.
One example is Apus the Bird of Paradise which unfortunately
like many of these modern constellations contains few if any bright stars.
Johann Bayer called the constellation Apus Indica the Indian Bird. That title
has been dropped today and it is just referred to as Apus.
Apus is what is called a circumpolar southern hemisphere
constellation, this means that from countries like Australia and New Zealand it
can be seen all year around. This is much like the familiar group of stars we
call the Plough which can be seen all year from countries such as Britain and
is called a northern circumpolar constellation.
This constellation is best seen in July which of course in
the southern hemisphere is during the winter.
Apus the bird of paradise was introduced to the sky in the
1590s by the Dutch astronomer and cartographer Petrus Plancius from the
observations of Dutch navigators Pieter Keyser and Frederick Houtman, when they
voyaged to the southern hemisphere and visited countries such as Indonesia or
what at that time was known as the Dutch East Indies.
Plancius had produced in 1589 a celestial globe using what
information was available regarding the southern stars. These included
constellations such as Crux the Southern Cross and Triangulum Australe the
Southern Triangle as well as the Magellanic Clouds which were called Nubecula
Major and Minor. These were reported by the Portuguese explorer Ferdinand
Magellan c 1480-1521 as he journeyed around the world. These we know today are
nearby Large and Small Magellanic Clouds which are nearby galaxies to our own
Milky Way Galaxy.
Plancius knew that the Dutch navigators Pieter Keyser and
Frederick Houtman would be travelling to the southern hemisphere so he met them
and trained them to draw and note features in the sky so he could replicate
them on a new star globe he was producing. With the knowledge that Keyser and
Houtman provided Plancius in either 1597 or early 1598 produced a new celestial
globe with an additional 12 constellations. None of these can be seen from
Britain and they describe mostly animals and subjects that travellers of the
day had seen as they explored the southern hemisphere.
The name of the constellation is derived from the Greek word
apous, which means “footless.” (Birds of paradise were at one point in history
believed to lack feet). The Greater Bird of Paradise known in India had a
magnificent white, yellow and red plumage but unsightly legs, which were cut
off by the natives desiring to offer the white man only the attractive part of
the bird. There are no myths associated with the constellation.
In China the constellation was referred to as E Cho the
Curious Sparrow or the Little Wonder Bird.
Apus is located near the south pole star, there are no
bright stars in Apus, the brightest are alpha at magnitude 3.8 and is around
430 light years away. The sky must be clear and dark to see this star. It is a K class giant star with a surface
temperature of around 4,000 degrees it is cooler than the Sun.
Apus is an example of a constellation where using Johann
Bayer’s Greek alphabet sequence does not work. This is because the second
brightest star is gamma with a magnitude of 3.9 compared to the brightness of
beta which is magnitude 4.2.
Although the Milky Way flows through Apus there are no
bright clusters of stars to be seen. The brightest is NGC 6101 a globular
cluster lying around 50,000 light years away. However, at magnitude 9.2 a telescope
would be needed to see it.
www.theramblingastronomer.co.uk
